Electrostatic inkjet head having spaced electrodes

Abstract

An electrostatic inkjet head has first and second electrodes. The first electrode is supported on a substrate and the second electrode is on a diaphragm so that a gap is formed between the first and second electrodes. A drive circuit is connected to the first and second electrodes to apply a voltage or pulse between the electrodes. When a voltage is applied between the electrodes, an electrostatic attraction force is generated between the electrodes. The attraction force displaces the diaphragm toward the substrate. This displacement of the diaphragm is used for the ejection of ink. Also, when the voltage is turned off, opposing central portions of the first and second electrodes define a gap that is greater than that defined by opposing end portions of the first and second electrodes. On the other hand, when the voltage is turned on, the opposing central portions of the first and second electrodes define another gap that is substantially equal to that defined by the opposing end portions of the first and second electrodes.

What is claimed is:  
     
       1. An electrostatic inkjet head, comprising: 
       a first electrode;  
       a substrate supporting said first electrode;  
       a second electrode spaced apart from said first electrode;  
       a diaphragm supporting said second electrode; and  
       a drive circuit connected with said first and second electrode for applying a voltage between said first and second electrodes so that an electrostatic attraction force is generated between said first and second electrodes, wherein said electrostatic attraction force results in a displacement of said diaphragm toward said substrate and said displacement is utilized for an ejection of ink;  
       wherein said first and second electrodes are positioned so that, when said voltage is turned off, opposing central portions of said first and second electrodes define a gap that is greater than that defined by opposing end portions of said first and second electrodes and, when said voltage is turned on, said opposing central portions of said first and second electrodes define another gap that is substantially equal to that defined by said opposing end portions of said first and second electrodes.  
     
     
       2. An electrostatic inkjet head in accordance with claim  1 , wherein said central portion of said first or second electrode is recessed. 
     
     
       3. An electrostatic inkjet head in accordance with claim  1 , wherein said central portion of said first or second electrode is recessed stepwise. 
     
     
       4. An electrostatic inkjet head in accordance with claim  1 , wherein said central portion of said first or second electrode is recessed to draw a curve. 
     
     
       5. An electrostatic inkjet head, comprising: 
       a first electrode  
       a substrate supporting said first electrode;  
       a second electrode spaced apart from said first electrode;  
       a diaphragm supporting said second electrode; and  
       a drive circuit connected with said first and second electrode for applying a voltage between said first and second electrodes so that an electrostatic attraction force is generated between said first and second electrodes, wherein said electrostatic attraction force results in a displacement of said diaphragm toward said substrate and said displacement is utilized for an ejection of ink;  
       wherein at least one of said first electrode and said second electrode is divided into plural parts so that each of said plural parts is electrically disconnected from the others of said plural parts and the plural parts of one of said electrodes are at different distances from the other electrode.  
     
     
       6. An electrostatic inkjet head in accordance with claim  5 , wherein each of said divided parts is not overlapped with another part. 
     
     
       7. An electrostatic inkjet head in accordance with claim  5 , wherein each of said divided parts is entirely or partially overlapped with another part. 
     
     
       8. An electrostatic inkjet head in accordance with claim  7 , wherein neighboring overlapped parts are electrically disconnected by an insulative material disposed between said neighboring overlapped parts.